US4971772A - High-purity lining for an electric low shaft furnace - Google Patents

High-purity lining for an electric low shaft furnace Download PDF

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Publication number
US4971772A
US4971772A US07/485,758 US48575890A US4971772A US 4971772 A US4971772 A US 4971772A US 48575890 A US48575890 A US 48575890A US 4971772 A US4971772 A US 4971772A
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United States
Prior art keywords
graphite
furnace
silicon
lining
reaction chamber
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Expired - Fee Related
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US07/485,758
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English (en)
Inventor
Hubert Aulich
Friedrich-Wilhelm Schulze
Benedikt Strake
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Siemens AG
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Siemens AG
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/08—Details peculiar to crucible or pot furnaces
    • F27B14/10—Crucibles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D1/00—Casings; Linings; Walls; Roofs
    • F27D1/0003—Linings or walls
    • F27D1/0006—Linings or walls formed from bricks or layers with a particular composition or specific characteristics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/90—Apparatus characterized by composition or treatment thereof, e.g. surface finish, surface coating

Definitions

  • the present invention is directed to an inside lining for a reaction chamber of an electric low shaft furnace, having a graphite melting crucible and a thermal insulation, and in particular to such linings wherein high purity silicon is produced by carbothermic reduction.
  • silicon produced pursuant to the Siemens C-process metallurgical silicon manufactured by the reduction of silicon dioxide with carbon is converted into a volatile silicon halide compound, cleaned via the vapor phase, and again reduced to silicon with hydrogen.
  • silicon produced through this process meets the high purity requirements needed for such uses as electronic silicon, it is to expensive for use in many other applications such as, for example, in photovoltaics.
  • the pre-cleaned initial materials are reacted with one another in an arc furnace.
  • the reaction of the pre-cleaned initial materials is based on what is referred to as the ACR process (advanced carbothermic reduction).
  • FIG. 1 illustrates schematically, a crossection of a known structure of an electric low shaft furnace that can be used to produce high-purity silicon.
  • the structure essentially comprises a melting crucible 1 composed of high purity graphite or carbon, a discharge aperture 2 that is likewise lined, and a heat resistant thermal insulation 3.
  • the thermal insulation is typically composed of refractory rock or of compounds based on silicon dioxide or, respectively aluminum oxide.
  • a further carbon layer 4 is provided under the melting crucible for thermal insulation.
  • a furnace jacket is provided formed by sheet steel 5.
  • the melting crucible 1 cannot be made silicon tight. This is true even when a highly compressed graphite is used as the crucible material 1. This is due to the high seepability of the silicon melt.
  • the silicon melt filters into the thinnest seams and enters into contact with the insulation material 3 therein.
  • the insulation material has a high phosphorous content because binding agents containing phosphorous are used to manufacture the insulation material.
  • the phosphorous is reduced out of the insulation material and is absorbed by the molten silicon.
  • the silicon which has become n-conductive due to the phosphorous content, is thereby rendered unsuitable for the manufacture of solar cells and must be cleaned of phosphorous. This is an involved process.
  • oxide ceramic materials for thermal insulation that exhibit an adequate purity, good insulating properties, and an adequate stability in a highly reducing furnace atmosphere are not commercially obtainable.
  • the present invention provides a high-purity lining for an electrical furnace, for an ACR process, that avoids the deficiencies set forth in the background of the invention, is cost-beneficial, and has good insulating properties at the same time.
  • the present invention provides an inside lining for a reaction chamber of an electric low shaft furnace, particularly for producing high-purity silicon from silicon oxide by carbothermic reduction, having a graphite melting crucible and thermal insulation, the floor of the reaction chamber includes an inside lining of high purity carbon.
  • the thermal insulation is composed of graphite, graphite grits, or lampblack. These materials replace the prior standard ceramic oxide materials. These materials differ greatly in terms of their thermal conductivity, which decreases from graphite to graphite grits to lampblack. Accordingly, in an embodiment, a multilayer format of the furnace lining is provided.
  • the inside lining is constructed from a high purity carbon that exhibits a boron content and phosphorous content each having a maximum of 0.05 ppmw and has an overall ash content of a maximum of 10 ppmw.
  • the inside lining is situated only in the floor region of the reaction chamber and the remaining side walls of the furnace are coolable.
  • the thermal insulation of high purity carbon is present in a plurality of different layers.
  • the inside lining of the furnace has three layers that, from inside towards outside, are of the materials graphite, graphite grits, and lampblack.
  • the graphite layer has a thickness that is such that, during operation of the furnace, the temperature therein decreases towards the outside from the interior operating temperature of the furnace down to below the melting point of the silicon.
  • the side wall of the furnace is cooled and the thermally insulating Iining of the side wall is eliminated.
  • FIG. 1 illustrates, schematically, a cross section of a known electric low shaft furnace.
  • FIG. 2 illustrates, schematically, a cross section of an embodiment of the inside lining of a furnace according to the present invention.
  • FIG. 3 illustrates, schematically, a cross section of another embodiment of the inside lining of a furnace according to the present invention.
  • the present invention provides an inside lining for the reaction chamber of an electric low shaft furnace, particularly for producing high-purity silicon from silicon oxide by carbothermic reduction having a graphite melting crucible and thermal insulation, at least the floor of the reaction chamber has an inside lining of high-purity carbon.
  • the structure includes an innermost layer 1 which should be as impenetrable as possible to the silicon melt, the innermost layer l is composed of electrographite blocks that exhibit an adequately high density. This functions to coat the silicon melt with a tight silicon carbon skin upon contact.
  • a porous graphite material is selected, a deeper penetration of the silicon into the porous graphite structure results and, as a consequence thereof, leads to a bursting of the structure due to the formation of silicon carbide. In addition to higher silicon losses, such a bursting of the structure also leads to a great graphite erosion.
  • a graphite grits layer 6 is provided as the next layer under the innermost layer 1.
  • An outermost layer 7 is provided after the graphite grits layer 6.
  • the outermost layer 7 can be composed of lampblack.
  • graphite grits 6, exhibit adequate stability and therefore, for example, can support the weight of an entire furnace fill as the thermal insulation of the floor of the melting crucible without losing its structure-induced, beneficial thermal insulation properties.
  • the thickness of the individual wall layers 1, 6, and 7 is determined in accordance with the desired thermal insulation.
  • the temperature at the innermost graphite layer 1 should drop off to about 1350° C., i.e., below the melting point of silicon. This temperature drop off thereby avoids a deeper penetration of the silicon melt into the innermost graphite layer 1, up to the insulating layer 6 and 7, thus preserving the layers insulating effect and avoiding an undesired loss of silicon material.
  • the carbon materials are provided in such high purity that given an allowable content of a maximum of 0.05 ppmw each of boron and phosphorous and given an overall impurity or ash content of a maximum of 10 ppmw, no further contaminations of the molten metal, for example of the silicon in the ACR process, arises due to the furnace lining.
  • the side walls of the furnace do not include an inside lining of thermally insulating material. Instead, the steel jacket forming the outer side wall 8 of the furnace can be cooled.
  • the crucible wall is then formed by the utilized of batch materials 9 Specifically, the crucible wall is formed by the batch mixture of SiO 2 and a reduction agent for example, lampblack brikettes). This batch mixture 9 remains in a solid condition at the edge of the crucible and will "bake” further due to the condensation of the silicon oxide formed in the reduction process. The silicon oxide is still volatile at these temperatures and will, thus, further solidify.
  • thermal losses that are slightly higher than those found in the embodiment having side wall insulation occur during operation.
  • the slightly higher thermal losses occur because the heat is predominantly eliminated by the metal melt, in a downward direction.
  • the crucible floor is thermally well-insulated with the layers 1, 6, and 7.
  • Silicon produced by the ACR process in the electric low shaft furnace of the present invention exhibits improved purity compared to silicon produced in traditionally lined furnaces. Remaining impurities are now dependent on the educts of the reduction process. Silicon produced in a make-up, for example, exhibits p-conductivity given a boron content of below 1 ppmw and is not compensated. Solar cells manufactured therefrom achieve efficiencies of more than 11%.
  • the furnace lining of the present invention provides good thermal insulation, is resistant to the smelt and operating conditions of the furnace and allows a continuous operation of the furnace over several years.
  • the furnace is thereby designed not only for the production of high purity silicon but can also be used for all other metalurgical processes wherein high-purity metals are to be produced by reduction.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Silicon Compounds (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Details Of Garments (AREA)
  • Footwear And Its Accessory, Manufacturing Method And Apparatuses (AREA)
US07/485,758 1987-09-23 1990-02-26 High-purity lining for an electric low shaft furnace Expired - Fee Related US4971772A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19873732073 DE3732073A1 (de) 1987-09-23 1987-09-23 Hochreine innenauskleidung fuer einen elektroniederschachtofen
DE3732073 1987-09-23

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US07236845 Continuation 1988-08-26

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US (1) US4971772A (ja)
JP (1) JPH01107089A (ja)
DE (1) DE3732073A1 (ja)
NO (1) NO884194L (ja)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5126112A (en) * 1989-07-18 1992-06-30 Hemlock Semiconductor Corporation Graphite and carbon felt insulating system for chlorosilane and hydrogen reactor
US6287381B1 (en) * 1991-08-22 2001-09-11 Raytheon Company Crystal growth process for large area GaAs with controllable resistivity and infrared window/dome with EMI-EMP protection formed therefrom
US6413601B1 (en) * 1998-10-23 2002-07-02 Graftech Inc. Thermal insulating device
US20070217988A1 (en) * 2006-03-15 2007-09-20 Amendola Steven C Method for making silicon for solar cells and other applications
US20080193363A1 (en) * 2004-08-20 2008-08-14 Mitsubishi Chemical Corporation Metal Nitrides and Process for Production Thereof
US20090188426A1 (en) * 2008-01-29 2009-07-30 Green Energy Technology Inc. Crystal-growing furnace with heating improvement structure
CN102924103A (zh) * 2012-11-22 2013-02-13 四川广汉士达炭素股份有限公司 一种炭砖及其制造方法与应用
CN102980397A (zh) * 2011-09-05 2013-03-20 鞍钢集团工程技术有限公司 一种石墨坩埚
CN101646621B (zh) * 2007-02-14 2013-11-06 法国原子能委员会 硅提纯设备

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10251076B4 (de) * 2002-11-02 2005-09-15 Schott Ag Schmelztiegel und Verfahren zu seiner Herstellung
EP2530051A1 (en) * 2011-06-03 2012-12-05 Evonik Solar Norge AS Reduction furnace body
CN108002379B (zh) * 2017-12-15 2021-02-12 吉林市巨邦炭素有限公司 一种增加炭黑循环使用次数的方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227431A (en) * 1961-11-22 1966-01-04 Nat Res Corp Crucible externally lined with filamentary carbon
US4247528A (en) * 1979-04-11 1981-01-27 Dow Corning Corporation Method for producing solar-cell-grade silicon
US4262039A (en) * 1975-12-05 1981-04-14 Kernforschungsanlage Julich Gesellschaft Mit Beschrankter Haftung Pyrolytic gas method of coating graphitic or ceramic articles with solids
US4390504A (en) * 1979-02-21 1983-06-28 Ibigawa Electric Industry Co. Ltd. Apparatus for producing silicon carbide consisting mainly of β-type crystal
DE3215081A1 (de) * 1982-04-22 1983-11-03 Siemens AG, 1000 Berlin und 8000 München System zur uebertragung von informationstelegrammen
US4460556A (en) * 1982-04-29 1984-07-17 Siemens Aktiengesellschaft Method for producing high purity Si for solar cells
US4820341A (en) * 1985-05-21 1989-04-11 International Minerals & Chemical Corporation Process for producing silicon or ferrosilicon in a low-shaft electric furnace

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227431A (en) * 1961-11-22 1966-01-04 Nat Res Corp Crucible externally lined with filamentary carbon
US4262039A (en) * 1975-12-05 1981-04-14 Kernforschungsanlage Julich Gesellschaft Mit Beschrankter Haftung Pyrolytic gas method of coating graphitic or ceramic articles with solids
US4390504A (en) * 1979-02-21 1983-06-28 Ibigawa Electric Industry Co. Ltd. Apparatus for producing silicon carbide consisting mainly of β-type crystal
US4247528A (en) * 1979-04-11 1981-01-27 Dow Corning Corporation Method for producing solar-cell-grade silicon
DE3215081A1 (de) * 1982-04-22 1983-11-03 Siemens AG, 1000 Berlin und 8000 München System zur uebertragung von informationstelegrammen
US4528667A (en) * 1982-04-22 1985-07-09 Siemens Aktiengesellschaft System for the transmission of information messages
US4460556A (en) * 1982-04-29 1984-07-17 Siemens Aktiengesellschaft Method for producing high purity Si for solar cells
US4820341A (en) * 1985-05-21 1989-04-11 International Minerals & Chemical Corporation Process for producing silicon or ferrosilicon in a low-shaft electric furnace

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
H. A. Aulich et al, Solar Grade Silicon Prepared by Advanced Carbothermic Reduction of Silica, Siemens Forsch. U. Entwickl. Ber. Bd. 15 (1986), No. 4, Springer Verlag, 1986, pp. 157 162. *
H. A. Aulich et al, Solar-Grade Silicon Prepared by Advanced Carbothermic Reduction of Silica, Siemens Forsch.--U. Entwickl.--Ber. Bd. 15 (1986), No. 4, Springer-Verlag, 1986, pp. 157-162.

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5126112A (en) * 1989-07-18 1992-06-30 Hemlock Semiconductor Corporation Graphite and carbon felt insulating system for chlorosilane and hydrogen reactor
US6287381B1 (en) * 1991-08-22 2001-09-11 Raytheon Company Crystal growth process for large area GaAs with controllable resistivity and infrared window/dome with EMI-EMP protection formed therefrom
US6413601B1 (en) * 1998-10-23 2002-07-02 Graftech Inc. Thermal insulating device
US6770161B2 (en) * 1998-10-23 2004-08-03 Advanced Energy Technology Inc. Method of making thermal insulating device by winding
US20080193363A1 (en) * 2004-08-20 2008-08-14 Mitsubishi Chemical Corporation Metal Nitrides and Process for Production Thereof
US8568683B2 (en) * 2006-03-15 2013-10-29 Steven C. Amendola Method for making silicon for solar cells and other applications
US20070217988A1 (en) * 2006-03-15 2007-09-20 Amendola Steven C Method for making silicon for solar cells and other applications
US7922989B2 (en) * 2006-03-15 2011-04-12 Amendola Steven C Method for making silicon for solar cells and other applications
US20110176984A1 (en) * 2006-03-15 2011-07-21 Amendola Steven C Method for making silicon for solar cells and other applications
CN101646621B (zh) * 2007-02-14 2013-11-06 法国原子能委员会 硅提纯设备
US20090188426A1 (en) * 2008-01-29 2009-07-30 Green Energy Technology Inc. Crystal-growing furnace with heating improvement structure
CN102980397A (zh) * 2011-09-05 2013-03-20 鞍钢集团工程技术有限公司 一种石墨坩埚
CN102924103A (zh) * 2012-11-22 2013-02-13 四川广汉士达炭素股份有限公司 一种炭砖及其制造方法与应用

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Publication number Publication date
NO884194L (no) 1989-03-28
DE3732073A1 (de) 1989-04-06
JPH01107089A (ja) 1989-04-24
NO884194D0 (no) 1988-09-21

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